Specific posts/pages from a child blog on the homepage

Maybe this question has been answered before, but I can’t find the answer on older threads.

So, my question is really simple : how is it possible to get posts/pages from a specific blog (not the root one) in order to show them on the homepage of buddypress? (on buddypress.org, we have “Usefull Pages” that are pages from codex.buddypress.org, I’m searching for exactly the same behaviour…)